Filamentary microtapes



July 13, 1965 L. E- LEFEVRE FILAMENTARY MICROTAPES Filed June 29, 1960 INVENTOR. bye 5'. Le/E'we United States Patent 3,194,716 FILAMENTARY MHZROTAPES Lloyd E. Lefevre, Bay City, Mich, assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware Filed June 29, 1960, Ser. No. 39,562 1 Claim. (Cl. 161-194) This invention relates to a process for preparing novelty and decorative microtapes from filamentary articles of labyrinthian cross section. More particularly, it relates to such a process which provides novelty microtapes of essentially uniform peripheral dimensions. The invention likewise comprehends the novelty microtape so prepared.

The fabric designer has included novelty yarns and filaments in fabric constructions in an ever-increasing amount. The resultant fabrics usually have randomly isolated areas that difier in texture and frequently also in .Color from the main body of the fabric. Typical of such fabrics are the nubby, boucle upholstery fabrics now finding wide acceptance. The novelty yarns and filaments used in making these fabrics include filamentary structures having randomly disposed slubs, bulbous portions, or other irregularities. Other types of novelty yarns include those which are uniform in construction but which differ in bulk, structure, or other manner from the traditional yarn.

A filamentary article that is finding increasingly wide usage in many applications is a filamentary microtape having a cross section that is essentially oval or elliptical in peripheral silhouette. These filamentary microtapes are tapes or ribbons having the edges curled resulting in appearance in a series of layers separated by air. This curled portion appears in section as a spiral or a labyrinth. Thus, this cross-sectional configuration consists of opposite edge portions spirally curled and separated by a fiat central portion. A typical cross section is illustrated in FIGURE 2 of the appended drawings. These microtapes of such section may be used directly in conventional textile operations and when so used provide high covering power, have a low bulk density, and exhibit other beneficial results.

These filamentary microtapes of labyrinthian cross section have been prepared from known organic, thermoplastic, resinous materials. Thermoplastic microta-pes of this structure permit many operations, such as thermal forming, heat sealing, thermal embossing, thermal calendering, and the like, to be carried out on the fabrics. However, it would be desirable for extending the areas of utility of these thermoplastic microtapes if novelty microtapes of such cross section could be prepared.

Accordingly, it is the principal object of this invention to provide a process for preparing novelty filamentary microtapes of labyrinthian cross section.

It is a further object of this invention to provide such a process for preparing these novelty microtapes which are characterized as being essentially uniform in overall dimensions.

It is a still further object of this invention to provide such a process for preparing the novelty microtapes from organic, thermoplastic, resinous materials.

The above and related objects are achieved by means of the process comprising the exposure of a filamentary microtape of an organic, thermoplastic, resinous material, said microtape characterized in having curled edge portions, to conditions of mechanical and thermal stress that will result in a differential strain between said curled edge portions and the central tape portion separating said curled edges. The invention likewise comprehends the novelty microtape prepared by said process and characterized in appearance by having the curled edge portions es- 3,l94,7lfi Patented July 13, 1%65 sentially unmodified in cross-sectional appearance from the microtape of which said novelty microtape is prepared and by having the central portion separating said curled edge portions exhibiting a shirred or wavy effect.

The tapes useful in the present method may be of any organic, thermoplastic, resinous material. As materials which may be advantageously used are the normally crystalline polymeric materials. These are the polymers which have a tendency to form crystallites or sites where small segments of a plurality of the polymer chains are oriented and held in position by secondary valence forces. This crystallite formation or crystallinity is usually visible when the polymers are examined by X-ray diffraction. Typical of the normally crystalline polymeric materials falling within the advantageous definition are the polymers and copolymers of at least 70 percent by weight of vinylidene chloride with the remainder composed of one or more other monoethylenically unsaturated comonomers exemplary of which are vinyl chloride, vinyl acetate, vinyl propionate, acrylonitrile, alkyl and aralkyl acrylates having alkyl and aralkyl groups of up to about 8 carbon atoms, acrylic acid, acrylamide, vinyl alkyl ethers, vinyl alkyl ketones, a'crolein, allyl esters and ethers, butadiene and chloroprene. Known ternary compositions also may be employed advantageously. Representative of such polymers are those composed of at least 70 percent by weight of vinylidene chloride with the remainder made up of, for example, acrolein and vinyl chloride, acrylic acid and acrylonitrile, alkyl acrylates and alkyl methacrylates, acrylonitrile and butadiene, acrylonitrile and itaconic acid, acrylonitrile and vinyl acetate, vinyl propionate, or Vinyl chloride, allyl esters or ethers and vinyl chloride, butadiene and vinyl acetate, vinyl propionate, or vinyl chloride and vinyl ethers and vinyl chloride. Quaternary polymers of similar monomeric composition will also be known. It has been found that the normally crystalline copolymers composed of from about 92 to 99 percent by weight of vinylidene chloride and correspondingly from 8 to 1 percent by weight of acrylonitrile or of a lower alkyl acrylate have suitable polymerization characteristics, are well adapted for use in the manipulative steps in this process, and result in exceptionally useful filamentary articles. For these reasons these vinylidene chloride-acrylonitrile and vinylidene chloride-lower alkyl acrylate copolymers represent preferred species for use herein. It should be understood, however, that the process is not limited to the treatment of normally crystalline polymers but that any non-elastic polymeric material may be employed. There are many materials, such as polyvinyl chloride and polystyrene, which are capable of forming continuous, coherent articles which are orientable but do not normally form crystallites. The polymeric materials, whether crystalline or noncrystalline, may also include minor amounts of monomers, such as vinyl pyrrolidone, vinyl oxazolidinone, vinyl alkyl oxazolidinone, and the like, which are known to aid the dye-receptivity and other properties of fibrous materials. Likewise, it is possible to use polymers having interpolymerized light and heat stabilizers. Also operable in the present method are tapes of polymeric materials,,such as the polyolefins, including, for example, polyethylene, polypropylene, copolymers of ethylene and propylene, and polyisobutylene. Equally useful in the method are the condensation polymers, such as the polyamides, including polyhexamethylene, diadipamide, and the polyesters, including polyethyleneterephthalate. Also of utility are the tapes and ribbons of rubber hydrochloride thermoplastic synthetic cellulose derivatives, including cellulose esters, such as cellulose acetate and cellulose others, such as methyl cellulose and hydroxypropyl methyl cellulose. It should be apparent that any organic, thermoplastic, resinous material which is capable of be- 3 ing formed into a flat tape or ribbon will find utility in the present invention.

The useful tapes from which the filamentary microtapes may be prepared are flexible tapes usually of about 0.001 to 0.005 inch in thickness and of about 0.1 to 1 inch in width. The thickness and width to be used in any given instance will depend in large measure upon the end product desired. The above limits are those which would normally be associated with the manufacture of fibers and laments. Wide sections of tape which are more accurately referred to as films are not easily fabricated into the requisite rnicrotapes and, consequently, are not readily adaptable for use in the present procedural steps. Howprecisely to filamentary microtapes formed from tapes of this 1-inch maximum, since useful articles may be prepared herefrom, although with less control of width and other characteristics than with the narrower tapes.

As earlier mentioned, the useful filamentary microtapes which may be employed in the present process are characterized byhaving a labyrinthian'cross section. An illustrative embodiment of a typical cross section meeting this definition is shown in FIGURE 2 of the appended drawings. These filamentary .microtapes that find use in the process may be prepared by a variety of methods. For example, a latex of a polymer as earlier described may be formed into an unfused, continuous, coherent coagulurn by the continuous, localized coagulation of that latex. That coagulum can then be slit into unfused tapes or ribbons, dried, and exposed to thermal means for fusing the coagulum into a tape or ribbon. It has been found that when the continuous, localized coagulation is formed by wetting a deposition base with a coagulant and then with the latex, there results a coagulum having a porosity gradient from one surface to the other. When the fusing heat is applied to the less dense surface of such a coagulum, it is found that the edges will roll over into the desired labyrinthian cross section.

Another method by which such filamentary microtapes may be prepared involves the passage of the aforementioned coagulum or of a fused tape or ribbon through mechanical shaping means, such as a groove, to impart a rolling action to the edge portions. This technique results in more exact control of the width, denier, and cross-sectional configuration of the microtape than the previously referred to unrestrained curling method.

As indicated, the presently claimed process involves the exposure of the filamentary microtape to conditions such that a differential strain between the curled edge portions and the flat, central portion is imparted. It is advantageous to the attainment of the desired result that the filamentary microtape exposed to these conditions be oriented prior to carrying out the present procedural sequence. In practical effect the orientation may be imparted essen tial strain. This differential strain may be achieved in one of two manners. The filamentary microtape may be exposed to heat against the fiat surface only while subjected to longitudinal stress. ie net result of this treatment is that the effective length of the central portion will be greater than that of the curled edge portions so that the central portion will exhibit a waviness relative to the unmodified edge portions.

The second manner of arriving at the desired product is to expose the curled edge portions only to heat, while said filamentary microtape is in essentially relaxed state so as to shrink the curled edge portions relative to the central portion.

The advantages and benefits of the process will be more apparent from the following description and the appended drawings which illustrate a preferred embodiment for carrying out the process. In the drawings;

FIGURE 1 represents in schematic outline a procedural sequence for arriving at thezdesired noveltymicrotapes,

FIGURE 2 represents a microtape of typical labyrinthian cross section, 1

FEGURE 3 represents a segment of the herein comprehended novelty microtapes, and

FIGURE 4 represents, in magnified elevation, the groove of a roll used in forming the desired filamentary microtapes.

In the embodiment illustrated in FIGURE 1, a fiat, fused and oriented tape orribbon 10 is passed around a first pair of snubbing rolls 11. The tape it is then passed through a fiat-bottomed groove having divergent side walls in a grooved roll 12. The filamentary microtape issues from said grooved roll 12 and is characterized by a labyrinthian cross section whose dimensions are dictated in large measure bythe size and shape of the groove relative to the tape. The filamentary microtape next passes over a heated bar or other heating' means 13 so as to heat either the curled edge portions only or the fiat, central portion only. The heated microtape then passes about a second series of snubbing rolls 14. And finally, to suitable collecting means (not shown).

When the filamentary microtape is disposed in the manner illustrated in FXGURE 1 so that the fiat, central portion is heated relative to the curled edge portions, then snubbing rolls 14 are operated at a peripheral speed at least slightly greater than the peripheral speed of snubbing rolls ill.

' When the heating means 13 is disposed on the reverse side of the microtape from that illustrated in FIGURE 1 so that only the curled edge portions are heated, then snubbing rolls l4 should be operated at slightly less than the peripheral speed of rolls 11 to permit the curled edge portions to shrink relative to the fiat, central portion.

Either of the above methods will permit attainment of A the desired novelty microtape having the appearance of tially simultaneously with the imposition of the ditlerenunmodified curled edge portions with a wavy, fiat, central portion.

It is also possible to employ an orientable tape in the process and apply a longitudinal stress on'the tape by means of the second snubbing rolls. 'In this case the tape will usually orient just prior to exposure to heat. During the heating period the portions of the tape that are heated will hot stretch Without appreciable orientation While the unheated portions will continue to orient.

The process has inanyadvantages and benefits. It is capable of continuous operation and of being fitted into an integrated scheme which would involve the microtapemaking process. The process is simple in operation, has few maninpulative steps, and requires no precision apparatus, such as is frequently needed with thermal extruszon processes. The product is characterized by essentially uniform dimensions, as contrasted with slubby yarns. Thus, the product not only presents a uniform appearance but also has uniform properties.

The operation of the process will be-more apparent from the following. illustrative example.

Example A latex of a copolymer of 97 percent vinylidene chloride and 3 percent acrylonitrile was continuously coagulated into a continuous coagulum, slit into ribbons of coagulum, dried, and fused. The resulting ribbon was inch wideland 0.002 inch thick.. The fusing took place over a heated cylindrical drum at 21 feet per minute. During this fusing the edges of the ribbon curled over, resulting in a cross sectional configuration similar to that of FIGURE 2. The ribbon was supercooled after fusing by passage at 23 feet per minute over a stainless steel roll maintained at 30 .C. The fused ribbon was snubbed between rubber snubber rolls at 30 feet per minute, fed over a heated freerturning roll maintained at. C. while being stretched 4 to 1 onto a heated snubber roll main- 5 tained at 145 C. During that period the ribbon was dis posed with the fiat side next to the roll. The novelty microtape Was then Wound in a 3.5 inch diameter core. The product had smooth curled edge portions with a Wavy central portion. The appearance was similar to that illustrated in FIGURE 3.

The process was repeated except that the ribbon Was passed over a heated bar maintained at 155 C. While being oriented at a stretch ratio of 4 to 1.

A similar rib'oon was oriented to a ratio of 4 to 1 and then passed over the heated roll with the curled edge portions facing the roll. The ribbon was maintained under minimum forwarding tension throughout. The resulting product Was similar in appearance to that above.

In like manner curled edge microtapes prepared from the normally crystalline vinylidene chloride copolymers with ethyl acrylate exhibited similar results.

What is claimed is:

A novelty microtape or labyrinthian cross section composed of an organic, thermoplastic, resinous material and characterized in having opposite edge portions inwardly curled uniformly about their longitudinal axis, said edge portions being separated by a Wavy, flat, central portion separating said curled edge portions.

References Steel by the Examiner UNITED STATES PATENTS Brandenberger 18-48 X Wade 154-46 Gibbs.

Graumann et al. 1854 Sisson et al. 28-82 Lowry et al. 18-48 Fantell.

Bourgeaux 1854 Frost.

Carr et'al. 18-54 Groombridge et a1 18*54 Rokosz.

Masters.

FOREIGN PATENTS ALEXANDER NY MAN, Primary Examiner.

EARL M. BERGERT, MICHAEL V. BRINDISI,

Examiners. 

